A member of the RMn₆Sn₆ rare-earth family materials, TbMn₆Sn₆, recently showed experimental signatures of the realization of a quantum-limit Chern magnet. In this work, we use quantum Monte Carlo (QMC) and density functional theory with Hubbard U (DFT + U) calculations to examine the electronic structure of TbMn₆Sn₆. To do so, we optimize accurate, correlation-consistent pseudopotentials for Tb and Sn using coupled-cluster and configuration–interaction (CI) methods. We find that DFT + U and single-reference QMC calculations suffer from the same overestimation of the magnetic moments as meta-GGA and hybrid density functional approximations. Our findings point to the need for improved orbitals/wavefunctions for this class of materials, such as natural orbitals from CI, or for the inclusion of multi-reference effects that capture the static correlations for an accurate prediction of magnetic properties. DFT + U with Mn magnetic moments adjusted to the experiment predict the Dirac crossing in bulk to be close to the Fermi level, within ~120 meV, in agreement with the experiments. Our non-stoichiometric slab calculations show that the Dirac crossing approaches even closer to the Fermi level, suggesting the possible realization of Chern magnetism in this limit.

RMn ₆ Sn ₆稀土族材料的一种成员 TbMn ₆ Sn ₆最近展示了实现量子极限陈磁铁的实验特征。在这项工作中，我们使用量子蒙特卡罗（QMC）和密度泛函理论与Hubbard U（DFT +  U）计算来检查TbMn ₆ Sn ₆的电子结构。为此，我们使用耦合簇和配置相互作用 (CI) 方法优化 Tb 和 Sn 的准确、相关一致的赝势。我们发现 DFT +  U和单参考 QMC 计算与元 GGA 和混合密度泛函近似一样，都会遭受对磁矩的高估。我们的研究结果表明需要改进此类材料的轨道/波函数，例如 CI 的自然轨道，或者包含捕获静态相关性的多参考效应，以准确预测磁性。根据实验调整 Mn 磁矩的DFT +  U预测狄拉克穿越整体接近费米能级，在 ~120 meV 范围内，与实验一致。我们的非化学计量平板计算表明，狄拉克穿越甚至更接近费米能级，这表明陈磁性在此极限下可能实现。